As the next-generation exposure technology adapted for miniaturization of semiconductor devices in the future, an extreme ultraviolet (EUV) technology using a very short wavelength of 13.5 nm is under consideration. However, this EUV technology is not mass produced due to the lack of a light source having adequate luminance Thus, there is a need to employ other approaches.
As such, multi-patterning methods based on exposure of ArF having a wavelength of 193 nm have been mainly applied. Among these methods, a patterning method called a self-align double patterning (SADP) has been widely used. As shown in FIGS. 9A to 9F, the SADP method includes: forming a pattern 102 having a pitch of S on an etching target layer 101 by photolithography (FIG. 9A); forming a first pattern 103 called a mandrel (core material) by slimming (FIG. 9B); forming a spacer 104 along the first pattern 103 (FIG. 9C); etching-back the spacer 104 (FIG. 9D); etching the first pattern (mandrel) 103 to form a second pattern 105 using spacers (FIG. 9E); and etching the etching target layer 101 using the second pattern 105 as a mask (FIG. 9F). Thus, an etching pattern 106 having a pitch of S/2 is obtained. That is to say, it is possible to obtain a pattern having a pitch of S/2 which is half the pitch of S formed with only photolithography. Further, a self-align quadruple patterning (SAQP) method capable of reducing the pitch by ¼ by repeating the SADP method once again is under consideration. As another multi-patterning method, there has been used an LEx method which repeats a litho etching method plural times (x times), such as a litho etch-litho etch (LELE) method which includes transferring an exposed pattern onto a hard mask of a substrate by etching, performing a secondary exposure at a position deviated by a pitch of ½, machining the hard mask.
These methods pose a noticeable problem in that it is difficult to control deviation and work precision due to the increased number of processes. For example, for the SADP method, there are two types of space portions (S) of a line-and-space (L/S) by nature. One of them is affected by a spacer film thickness deviation, an etching deviation and a lithography CD deviation. Thus, a CD deviation of the final space portion tends to increase. On the other hand, line portions L are affected by only the spacer film thickness deviation and the etching deviation. Specifically, as shown in FIG. 10, all the line portions L1 correspond to the width of the spacer 104, and their deviation depends only on the film thickness of the spacer 104 and etching. In contrast, for the space portions, there are two types, i.e., a first space S1 corresponding to the first pattern 103 and a second space S2 corresponding to a space between adjacent spacers 104. A deviation of the first space S1 depends only on lithography CD and etching, whereas a deviation of the second space S2 depends on lithography CD, spacer film thickness and etching.
At present, a semiconductor device wiring process mainly uses Cu wiring using a damascene structure. In this case, a space portion formed by the SADP method becomes a wiring portion. That is to say, this means that a deviation of the wiring portion increases. This situation is caused even in the SAQP method and the LEx method.
However, in the wiring process, there are many cases where the deviation of the wiring portion is more problematic than a deviation in an insulating portion. Therefore, an inversion method which is capable of minimizing the deviation of the wiring portion by inverting a line portion and a space portion is under consideration.
In addition, a typical inversion method inverts a line portion and a space portion through a series of processes including: forming an inversion material on a pattern, etching-back the inversion material, and etching away the original pattern. However, such a method includes a number of processes, which causes deviations. In addition, a problem occurs in that work controllability is difficult. Therefore, such an inversion method is not actively practiced in reality.